Casting of rare earth metals



diameter.

rum

. I oasrmd or Harold Marland Broadh urst, iiiverpool,

1 aasignor to Imperial Chemical Industries Lim ited, a corporation ofGreat Brl No Drawing. Appllcatio 543,950. In Great Britai tetra-20o) I vv pass over the surfaces of This invention relates to improvements incasting rare earth metals and alloys thereof. and to moulds therefor.

Rare earth metal alloys can be. cast into flints for pyrophoric lightersby pouring a molten alloy or mixture of iron and mischmetall, with orwith-.

out additions or small amounts oi other metals, into appropriately sizedmoulds constructed of a ferrous metal shaped to produce sticks oi smallinto small pieces for use. flints have a rough or unpolished surface andmay disintegrate on storage, possibly from attack by the atmosphere. .Ithas been proposed to 'cast rare earth metals from beneath a protectinglayer of molten salt into a mould dusted or otherwise coated withmagnesia or other inert material such as rolling scale or tin plating sothat the pieces of cast metal may be easily removed from the mould.

According to the present invention a process The sticks aresubsequently. broken Made in this way the g it July 7, 1944,

Serial ha areas 3 surface layers are oxidised to the black magneticoxide. The temperature of the air should be controlled so that the moulddoes not become too 'hot during the oxidation and cause general break upor loss of shape of the mould. The

moulds may then be allowed to cool and can then be used by pouring themolten alloy, for example an alloy of mlschmetall and iron, into themfrom a suitable container, and allowing the cast metal to cool oil. Itis also possible to cast the metal into the moulds before they havecooled completely, for example while they are still at a temperature ofthe order of 100 0., and the moulds for the production of rare earthmetal alloy flints suitable for pyrophoric lighters includes the step ofcasting the rare earth metal alloy in a ferrous metal mould the surfacelayers of which mould coming into contact with the molten alloy have ibeen converted by treatment under oxidising confrom the mould readbut inaddition the stability of the fiints in air is considerably increased,and the fiints have a more attractive appearance.

In one method or carrying out the invention the moulds are heated in avessel to a dull red heat and air is blown through the vesselso as toinvention it is not only and the casts may then be allowed to cooltogether. The sticks of metal as removed from the moulds are found tohave a smooth, almost black appearance, and have an improved resistanceto disintegration in the air.

Iclaim:

1. A process for the production of rare earth metal alloy flintssuitable for use in pyrophorlc lighters, and having improved resistanceto disintegration in the air which includes the step of casting the rareearth metal alloy in a terrous metal mould, the surface layers of whichmould coming into direct contact with the molten alloy have beenconverted by treatment under oxidising conditions to a substantiallycontinuous film of black iron oxide.

2. A process for the production of flints suitable for use in pyrophoriclighters. and having improved resistance to disintegration in the airwhich includes the step of casting an alloy of iron and mischmetall in aferrous metal mould the surface layers or which coming into directcontact with the molten alloy have been converted by treatment-underoxidising conditions to a substantially continuous film ofblack ironoxide. HAROLD MARLAND BROADHURST.

the mould until the

